The present invention relates to stitching machines, and more specifically, to computerized machines capable of stitching programmed designs into garments using multiple thread colors and presser foot assemblies associated therewith.
Stitching systems capable of stitching or embroidering patterns into garments or fabric using multiple colors are common in today""s garment industry. In typical stitching machines, a first needle stitches a first color in a preset pattern. If the pattern requires several colors, a second needle stitches a second color in a preset pattern, with this process repeated for several colors until the complete pattern is stitched into the garment. Such stitching or embroidery machines are commonly controlled by a computer system. Typically, an operator downloads a pattern to be stitched to a computer system within the embroidery machine. Included with the pattern are several other parameters, including the size of the pattern to be stitched, and the size of the hoop which will hold the garment while it is being stitched.
Upon receiving the pattern and associated other information, the embroidery machine makes appropriate calculations to, among other things, verify the pattern will fit on the garment or fabric, and that the pattern will not overlap the hoop. After the pattern is downloaded, the computer system makes the appropriate calculations. When the operator has loaded the garment or fabric onto the embroidery machine and made all of the appropriate checks, the operator gives the embroidery machine a command to begin stitching, at which point, the machine begins stitching the pattern into the garment or fabric.
Typical embroidery machines include a sewing head, an X-Y assembly, and a hook and bobbin assembly. The sewing head is commonly a multi-needle head, containing several needles which are used to stitch different thread colors. The sewing head is commonly located on a carriage at the front of the embroidery machine and is movable on the carriage to locate a first needle in a stitching position above the hook and bobbin assembly to stitch a first thread color into the garment. When a second thread color needs to be stitched into the garment, the sewing head is moved on the carriage to locate a second needle in a stitching position above the hook and bobbin assembly to stitch the second thread color into the garment.
When performing stitching operations, the embroidery machine, as is common and well known in the industry, moves the needle containing an upper thread through the garment. There is typically a needle plate located beneath the garment which the needle projects through when it has moved through the garment. Beneath the needle plate is the hook and bobbin assembly. The hook rotates around a lower thread which is fed from the bobbin. The hook rotates to catch the upper thread, and carries the upper thread around the lower thread as the hook rotates. When the hook nears the completion of its revolution, the needle is pulling back through the needle plate and garment, and the upper thread disengages from the hook. When the needle pulls the rest of the way through the garment, the upper thread is pulled around the lower thread and becomes taught, thus securing, or locking, the stitch. The X-Y assembly then moves the garment to an appropriate position for the next stitch, and the process is repeated.
The X-Y assembly is secured to the embroidery machine and is adapted to be connected to a hoop which contains a garment to be stitched. The X-Y assembly contains an X and a Y positioning mechanism which moves the hoop in both the X and Y directions with respect to the embroidery machine. When stitching a pattern, the X-Y assembly moves the hoop in a preset pattern with respect to the stitching needle, and a pattern in thus stitched into the garment.
In such systems, mechanical apparatuses typically pull thread from a spool through a take-up lever and to the needle assembly. The thread is fed through the needle, which, as discussed above, moves in a reciprocating manner to move the needle through the garment and into the hook and bobbin assembly. As described above, when the needle pulls out of the garment, and the stitch is locked, there is tension in the thread which pulls the thread taught and locks the stitch. However, typical systems create more tension than is required to lock the stitch. This extra tension is the result of the mechanical apparatuses that pull the thread from the spool to the needle. Typical embroidery machines, as well as other stitching machines, route thread from the spool to a thread guide, to a take up lever, back through the thread guide, and to the needle. The take up lever is connected to the same mechanical apparatuses which move the needle, and moves up and down with the same frequency.
When the take up lever moves back up, thread is pulled from the hook and bobbin, resulting in the extra thread tension. This extra thread tension may cause the fabric of the garment being stitched to xe2x80x9cbunch up.xe2x80x9d That is, the tension in the thread will create additional tension in the stitches being sewn into the garment and, if the fabric of the garment is a relatively soft material, the stitch may pull the fabric together. In situations where this may happen, it is common to use a backing material to lend additional support, or stiffness, to the garment in order to avoid this bunching up. The backing material is placed on the side of the garment opposite the side that the pattern is stitched on. The increased amount of material required for the backing increases cost, compared to stitching a garment using no backing. Thus, it would be advantageous to reduce the need for backing material. Additionally, the use of backing material also increases the labor required to stitch a pattern into a garment, compared to stitching a garment with no backing. When using backing, an operator must obtain the backing material, and place it into the proper position with respect to the garment being stitched. Additionally, once the pattern is stitched, the backing material may need to be trimmed by an operator. Therefore, the reduction of the need for using backing material would also reduce labor costs related to stitching patterns.
In addition to necessitating the need for backing material as described above, the extra thread tension created by the mechanical apparatuses, which pull thread from the spools to the needle assemblies, may lead to thread breaks, which can interrupt the stitching process. If the embroidery machine has a single sewing head, the stitching operations must be stopped and the thread break corrected. If the embroidery machine has multiple stitching heads, and a thread breaks on one of the stitching heads, it may be more difficult to correct the thread break. This is due to the multiple stitching heads operating synchronously, stitching the same pattern into multiple garments at the same time. When a thread breaks, it typically takes a machine several stitches to detect that the break has occurred. If a thread breaks on a first stitching head, the remaining stitching heads will continue stitching the pattern until the first stitching head stops. Since it is common for embroidery machines with multiple sewing heads to have the sewing heads mechanically coupled, when such a thread break occurs, the remaining sewing heads will be xe2x80x9caheadxe2x80x9d of the sewing head which had the thread break. Thus, when a break occurs in such a system, additional steps must be taken to xe2x80x9ccatch upxe2x80x9d the sewing head which had the thread break. Thus, it would be advantageous to reduce the number of thread breaks and to reduce the necessity to back up all the heads in the event of a thread break.
Additionally, in typical machines which employ mechanical apparatuses to pull thread from the spool, the amount of thread pulled from the spool for each stitch may not be consistent, due to geometrical variations which occur from stitch to stitch. This inconsistent amount of thread pulled from the spools results in differing thread tension from stitch to stitch, and may result in inconsistent sew-outs. Inconsistent sew-outs may result in a completed pattern that has less uniformity from stitch to stitch, and may thus reduce the aesthetic appeal of the stitched pattern. Therefore, it would also be beneficial to reduce thread tension and have just the right amount of thread in such a system in order to produce more consistent sew-outs to result in a consistent and visually appealing stitched pattern.
As mentioned above, embroidery systems may encounter thread breaks, where the upper thread being stitched from the spool and needle assembly may break. Additionally, a break may occur in the thread being used to lock the stitch using the bobbin and hook assembly, known as a lower thread break. Thread may break for a number of reasons, including tension in the sewing process, incorrect feeding into the system from the thread spool or bobbin, and binding in the mechanical apparatuses which pull the thread into the needle or hook assembly, to name a few. When performing stitching operations, it is beneficial to have knowledge of any thread breaks as quickly as possible, in order to discontinue the stitching of the pattern and repair the break and return the embroidery system to stitching operations.
Typical systems include sensors to perform the function of detecting thread breaks. Such systems commonly include a thread break monitor to detect upper thread breaks, and an underthread detector to detect breaks in the lower thread. The thread break monitor generally includes a mechanical assembly which detects movement in the upper thread. The thread break monitor is usually located at a position above the take up lever, and sends a signal to control electronics in the embroidery machine if there is no movement in the upper thread. When the control electronics receive a signal that the upper thread is not moving as expected, this indicates a problem with the sewing process such as a thread break, and the control electronics act to halt the stitching operations of the embroidery system. Likewise, the underthread detector is generally located in a position close to the hook and bobbin assembly, and includes a mechanical or optical apparatus to detect movement in the lower thread, and sends a signal to the control electronics in the event that the lower thread stops moving.
When the embroidery system halts stitching operations after a problem, such as a thread break, in the upper or lower thread, is detected, an operator may then repair the break and resume stitching operations. In such a system, it is beneficial to detect the thread break quickly in order to repair the break and resume operations with as little down time as possible. Such systems typically detect a break in the upper or lower thread within several stitch cycles of the break, with a typical number of stitches being five.
While current sensors for detecting thread breaks are adequate for detecting such breaks, they commonly have problems associated with them. In particular, underthread detectors can be problematic during operations of an embroidery system. As mentioned above, underthread detectors in typical embroidery systems are located in close proximity to the hook and bobbin assembly, and are mechanical or optical apparatuses which detect the break in the thread by sensing mechanical movement. Because of their location beneath the garment being stitched, it is common for debris to accumulate in or around the underthread detector. This may result in the underthread detector malfunctioning, and giving false readings of thread breaks or not detecting a thread break. In such a case, the underthread detector requires cleaning, or in certain cases, replacement. In addition to debris, lubricant from the mechanical apparatuses may also accumulate in and around the underthread detector, resulting in the sensor associated with the underthread detector malfunctioning, which can also result in the underthread detector having to be cleaned or replaced. Therefore, it would be advantageous to have a robust sensor which can detect breaks in the underthread with at least the same sensitivity as current underthread detectors, while also requiring less maintenance due to collected debris and lubricant in and around current underthread detectors.
In addition to the inadequacies of current underthread detectors, upper thread break sensors also have several problems commonly associated with them. One such problem is the location of the sensor. As mentioned above, upper thread break sensors are typically located above the take up lever on the embroidery system, and can often take several stitches to detect a thread break. Since it is advantageous to detect a thread break as quickly as possible, it would be advantageous to have a thread break detector which is closer to the needle, and can detect thread breaks relatively quickly.
As mentioned above, when a needle moves the upper thread into the garment when stitching, the bobbin and hook assembly lock the stitch by looping the lower thread around the upper thread prior to the needle lifting out of the garment. In order to prevent the garment from lifting from the needle plate, and to more securely lock a stitch, a presser foot is lowered to the garment surface to secure the garment during the stitching. The presser foot helps ensure that the stitch is properly locked and the tension in the thread is consistent from stitch to stitch.
In order to perform optimally, a presser foot must contact the garment surface when the needle lifts out of the garment. If the presser foot does not contact the garment surface, the garment may lift from the needle plate when the needle lifts through the garment, thus creating the potential for inconsistent sew-outs. Alternatively, if the garment is made of a relatively thick fabric, the presser fool may strike the garment with a relatively high force, creating a relatively loud audible sound, and causing mechanical stress in the presser foot, reducing its life-time. Thus, it is important to properly adjust the height of the presser foot such that it contacts the garment surface, yet does not contact with a force high enough to create a loud audible sound and/or mechanical stress. The loud audible sound is not desirable because, among other reasons, it is typically preferred that embroidery machines operate with as little noise as possible. Low noise operation is desirable especially when several embroidery machines are located in the same room, because additional noise may result in difficulty for people around the machines hearing other people or audible alarms. Thus, it is advantageous to have an adjustable presser foot, allowing proper force to be applied to garments of different thicknesses during stitching, as well as reducing noise level resulting from operation of the machine.
In typical current day machines, the presser foot is adjustable by manually adjusting a mechanical linkage connecting the presser foot to the needle drive assembly. This adjustment is typically done by removing safety covering associated with the needle drive and making an adjustment to the mechanical linkage to adjust the presser foot height. The safety cover is then replaced, and the embroidery machine operated. The operator then observes the operation of the machine to verify the presser foot is properly adjusted. If the presser foot is not properly adjusted, the adjustment process is repeated until the presser foot height is correct. As can be seen, this can be a laborious and time consuming process. As a result, many times the presser foot is improperly adjusted, or not adjusted at all. The presser foot may be improperly adjusted because an operator may make a first adjustment, and not make any additional adjustments to further fine tune the presser foot height, due to the burden of the adjustment process. In certain cases, the presser foot may not be adjusted at all, due to the burden of the adjustment process. Therefore, it would be advantageous to have a presser foot which is easily adjustable and can be adjusted without removing safety covering from the machine. Furthermore, it would be advantageous to make presser foot adjustments while the machine is operating, thus allowing for fine tuning of the presser foot height without interrupting stitching operations of the machine.
As mentioned above, a garment is placed in a hoop or other apparatus in order to secure the garment to the embroidery machine and to properly move the garment beneath the stitching head in order to stitch a pattern into the garment. Additionally, as also mentioned above, hoops of varying size may be used, depending upon the pattern and the garment that is being stitched. When a garment is placed in this hoop and secured to the X-Y assembly of the embroidery machine, it is important to ensure that the needle will not hit the hoop. If the needle hits the hoop, it can damage the needle and result in the embroidery machine being inoperable and needing repair. This results in downtime for the machine, as well as the cost of the replacement parts and labor to install the replacement parts.
Additionally, in many situations, it is beneficial for an operator to visually verify the location at which a needle will penetrate the garment. For example, when a garment is initially placed onto an embroidery machine, the starting location of the pattern is set in order to ensure the pattern is stitched at the proper location on the garment. Such a situation can also arise when an applique is stitched into a pattern. When the applique is to be set on the garment being stitched, the location of the stitch is determined in order to verify that the applique will be properly secured to the garment. Also, in the event of a thread break, once the thread break is corrected, the machine must be placed in the position to resume stitching from the point of the thread break. Typically, machines can be backed up a certain number of stitches, and the location verified, and stitching operations continued.
In typical embroidery machines, the control system includes software which verifies that the needle will not contact the hoop. This software receives information regarding the hoop size, and compares the pattern to be stitched to the hoop size to verify that no stitching will occur at or beyond the edge of the hoop. However, occasionally the hoop size entered into the software is not correct or the position of the pattern relative to the hoop is offset. In such a case, if the hoop actually placed onto the embroidery machine is smaller than the hoop that the control system thinks is there or if the pattern is offset, the needle may contact the hoop and cause damage. Accordingly, it is common for an operator to visually verify that the needle will not contact the hoop. In typical current day machines, this is commonly done by the operator pulling a needle down from the needle case to a location just above the garment, without actually contacting the garment. The embroidery machine is then commanded to trace an outline of the pattern to be stitched, and the operator visually verifies that the needle will not hit the hoop at any point of the pattern.
In situations where an operator needs to verify the starting location of a stitch, a similar procedure is used. Typically, an operator will pull a needle down from the needle case to a point just above the garment to be stitched. With the needle in this position, the location of the garment is adjusted until the proper starting location is located beneath the needle. Once the proper starting location is located beneath the needle, the needle is pushed back into the needle case, and stitching operations are started.
While the above-mentioned procedures are useful in verifying that a needle will not hit a hoop, and the starting location of a stitch, they have several drawbacks. One such drawback for using such a procedure to verify that a needle will not hit the hoop is that often the needle is pulled down far enough that, if the pattern does overlap the hoop, the hoop will contact the needle during the tracing procedure described above. In such a situation, an operator either has to stop the tracing, or push the needle out of the way, to prevent the needle from being damaged by hitting the hoop. Thus, if an incorrect hoop is on the embroidery machine, a needle may still be damaged even using the visual verification described above. Also, if a needle is pulled down too far, the garment may be damaged. Additionally, there are safety concerns with the procedures described above. Namely, an operator may be injured in the process of pulling a needle down from the needle case, or pushing the needle back into the needle case. Accordingly, it would be advantageous to verify the needle will not hit the hoop, and to verify the starting location of a stitch without an operator having to physically pull a needle down from the needle case to a point close to the garment. Furthermore, it would be beneficial to reduce the possibility of a garment being damaged during tracing by a needle that is pulled down.
As mentioned above, if mass producing garments it is beneficial to be able to stitch the same pattern into multiple garments. Such a situation is common, for example, when stitching logos into clothing. In such a case, it is useful to have several stitching heads operating simultaneously in order to increase production of such garments. It is also useful to use as few operators in such operations as possible, to reduce labor costs associated with stitching the patterns into the garments. One common method for achieving both of these objectives is to have multiple stitching heads which operate simultaneously to stitch patterns into multiple garments. Such machines typically are controlled at a single location by an operator after loading garments into each stitching head location. Many of these machines have stitching heads which are mechanically coupled to one another. In such a case, all of the stitching heads have to be used, due to the mechanical coupling of the stitching heads.
Additionally, these type of machines generally have a fixed number of heads, and if additional capacity is desired, an entire new machine must be purchased, often at considerable expense. Thus, it would be advantageous to have a machine which is capable of adding stitching heads incrementally, thereby allowing incremental capacity increases without as significant of a capital expense. Furthermore, it would be advantageous to, in certain circumstances, allow for fewer than all of the stitching heads on such a machine to be used, thus allowing for the stitching of a single or very few garments on such a machine.
Accordingly, there is a need for a stitching machine which overcomes the foregoing drawbacks found in prior art machines and meets the aforementioned needs.
In accordance with the present invention, a stitching apparatus is disclosed having a presser foot assembly with a presser foot, an adjustment element, and a linkage between the adjustment element and presser foot. The presser foot has a foot end and a connecting end. The linkage is connected to the connecting end of the presser foot, and is operable to change a travel distance of the foot end when the adjustment end is adjusted. The adjustment element is operable to be adjusted while the stitching machine is conducting stitching operations.
The linkage can include an adjustable cam in operative association with the adjustment element, the adjustable cam having a cam surface in operative association with a first end of a cam follower. The linkage can include a cam follower having a first end and a second end, with said second end engaging the presser foot, and when the cam follower moves, the presser foot moves substantially vertically. The linkage can also include a movable crank shaft, a reciprocator coupled to the crank shaft, and a reciprocator shaft guide, such that the reciprocator reciprocates along the reciprocator shaft guide when the crank shaft is moving. The cam follower can be pivotally coupled to the reciprocator, and the first end of the cam follower moves along the adjustable cam resulting in movement of the second end of the cam follower. The adjustment element can include a cam adjustment eccentric that, when moved, causes movement of the adjustable cam in a radial direction and, when the adjustable cam is at a first radial distance from the cam follower the presser foot travels a first distance, and when the adjustable cam is at a second radial distance from the cam follower the presser foot travels a second distance.
The invention, in one embodiment, also includes a method for adjusting a presser foot assembly that includes a presser foot in a stitching machine. The method includes the steps of stitching a pattern in fabric using the stitching machine, and adjusting a pressure that the presser foot applies to the fabric during the stitching step. The adjusting step can include moving a cam follower using a cam that is moved by an adjustment element. The adjusting step can also include engaging the presser foot using the cam follower. The adjusting step can also include moving a reciprocator substantially vertically with the cam follower pivotally connected to the reciprocator. A crank shaft may cause movement in the reciprocator.
Based on the foregoing, several benefits of the present invention are readily seen. The invention provides an apparatus which is capable of adjusting the pressure applied to the fabric by a presser foot while the stitching machine is operating. The apparatus provides an adjustment mechanism which is relatively easy to operate, and consumes relatively little time to make a proper adjustment.
Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings.